* I feel terrible/awful/sick: This is the most common meaning, and it's used to express a feeling of general unwellness.
* I'm really bad: This can be used to express a feeling of being very ill, or it can be used figuratively to express feeling very bad about something.
* I'm in a terrible state: This is a more formal way of saying "I'm feeling really bad."
Here are some examples:
* "Estoy fatal, me duele mucho la cabeza." (I feel terrible, my head hurts a lot.)
* "Estoy fatal con este trabajo, no lo soporto." (I'm really bad with this job, I can't stand it.)
* "Mi coche está fatal, no funciona." (My car is in a terrible state, it doesn't work.)
It's important to consider the context of the situation when translating "estoy fatal" into English.